Tire pressure gauge



Nov. 13,1928. 1,691,441

' J. E. KENNEDY ET Ai.

TIRE PRES SURE GAUGE Filed Aug. 8, 1925` flo Patented Nov. 13, i928.

entre!) STATES PATENTfoFFlcE.

TIRE PRESSURE GAUGE.

Application filed August B, 1925. V'Ser'al No. 48,977.

This invention relates to pressure gauges and particularly that type of pressure gauge that is adapted to temporary application to pneumatic tires to test the degree of 'air pressure present in any tire.

Heretofore commercial pressure A gauges for this purpose have employed, as the air actuateol element, either an elongated eX-v tensible rubber tube dependent on the elasticity or stretch of the rubber, or a Bourdon tube dependent on the spring or elasticity of a curved tube, but both these `constructions are open to serious practical faults. Asrubber when it remains stretched or uistended rapidly deteriorates the coefficient of elasticity changes and the device, if approxi# mately accurate when new, becomes increasine'lv inaccurate the longer it is used; The Bduidon tube devices, while more accurate at first than the extensible elastic tube,` are verv ser ive and quickly rendered useless by careles handling a'nd'tumbling about'in a tool kit. Devices with a close fitting movable air tight piston are not comn'iercially' used because the friction ynecessary to make a leali-proof pistonis so great as to prevent evenap proximate accuracy of pressure reading.

The object of the present invention is to overcome these diflicult-ies by providing a pressure-testing gauge that when properly A is and remains accurate for an inie period of time despite theordinary rough usage to which such devices are comv subjected, and a further ob]ect41s .to v1de a device ofthis kind which will itain its pressure readin 0 Vafter being ap plied to and removed from ltire so that'it is unnecessary to closely inspect the same in the ious positions it must assume when applicfil to tire stems in the different positions in which they stand when the caris at rest, These purposes are-realized by the em pl ynicntof movable air-sealing means that is completely responsive to variations in air pressure. thus affording accuracy, and that is not dependent on properties that are 1mpaired by deterioration or carelesshandling, and is not required to overcome substantial frictional resistance in order to function.

With these and otherobjects in view the invention comprises, in combination with an air pressure chamber adapted to admit compressed air in the'tire, of a .tubular air-sealing diaphragin of flexible fabricV secured to said chamber to be collapsible and extensible endwise independently of the stretch of material, and of a freely movable springpressed plunger arranged to oppose a counter-balancing thrust against the airpressedend of said diaphragm and acting to move a pressure-indicating member over a pressure scale in accordance with variations in the aii` pressure of the tire. Another feature of the invention resides in the construction and arrangement by which a freely m0v able plunger is employed to maintain a pressureV reading after the gauge has been removed from its application to the tire, the indicator member being connected with the plunger so as to be `movedthereby in bot-h directions. Another feature of the inif'ention consists inl'a construction and arrangement whereby the compressed airv admitted from the tire is retained in the device'to preserve the pressure reading after the device has been removed from the tire, while permitting return of tho pressure gauge to initial position at will. I

rlhese and other `features of the invention will be described in the'following specifica-r tion and will be defined in annexed. f

In the accompanying drawings we have illustrated specilic embodiments ofthe principles of this invention, in which: f

Figure'l is a front elevation of the complete the claims hereto ypressure gauge, a part of the face Vbeing broken away to showthe interiOr plunger mechanism.

Figure 2 is a central vertical section through the device shown Ain Figure l.

Figure 3 isa detail vieuT showing, in elevation, the collapsible air-sealing,diaphragm.

`Figure 4l is a vertical central section showing amodilicd formrof pressure indicator and ofV air-trapping and releasingdevice. y F in'ure 5'is a detail View showing, in elevation, the form'of indicator shown in Figure 4. Figure 6 is a transversevsection through the inlet port and the valve shown in Fig. vl.. y Figure 7 shows the supporting rings of the tubular diaphragm. f

The forms of the invention illustrated in the drawings employ, for the admission of air to the interior of the pressure` gauge, a?v scat adapted to form simply a pressure Contact with the tire nipple Without using a threaded coupling, but it will be understood that any form of air-tight connection bet-Ween the de vice and the nipple of the tire stem may be employed.

'munication through the duct or passage' 1C With the interior air chamber of the pressure gauge.

As it is more convenient, when testing a tire, to preserve the pressure gauge reading for easy inspect-ion after the'gaugehas been removed from the tire, provision hasV been made, in this case', for trapping the com,- pressed air admitted into the gauge from the tire so aste preserve the pressure reading, after Which the confined air may berelcased to allow the gauge to return to initialposition. y Y

Accordingly, We have provided an inlet valve 3, constructed and arranged to permit manual conti'ol to open or close the valve at Will and preferably act-ing to remain open or closed until shifted manually to the other po,-

sition. As shown in Figures 4, 5 and 6, the valve 3 has an elongated cylindrical stem snugly iitted to slide in a longitudinal bore 1U, forming thevalve chamber or recess, and has an enlarged tapered or conical flared end, preferably covered with rubber, and adapted to snugly Contact with a similar conical valve seat surface forming the inner end of the valve chamber. At one side of the valve chamber 1b the cylindricalvyvall thereof is longitudinally grooved, as at 1C, to afford communication to a lateral inlet duct 2, formed in part by a headed nut l, having threaded engagement with the part 1'LL and bored to admit air into the lateral passage. This bored nut servesfboth to retain the seat washer` 5,

which is formed to be pressed against the end of the tire valvenipple, and the nut also provides a proyection to engage and unseat the tire valve when the gauge is pressed firmly against the tire stem nipple With the rubber Washer 5 in snug contact to admit air into the gauge, Without external leakage.

The valve 3 may normally remain open to admit air, but after application of the gauge to the tire stem the valve is closed by a suitable finger-actuated button or shifting inemn bei' comprising, in this case, a frictional slide 6 through which is passed a pin or screwv 6, which projects inwardly through a narrow elongated slide 1d to engage or connect'with the valve stem, suoli screw forming an actuating connection between the sliding button and the valve stem land also serving to retain the button in place. Y

When it is desired to take the pressure reading,the ga.uge,with the valve in open position, is pressed against the tirefnipple with the yielding seat 2 pressed against the end of the tire stem nipple, thus unseating the tire valve and establishing communication between the interior of the tire and the air cliamberinside the body or casing of the pressure gauge.

Before the gauge is Withdrawn from pressure y contact With the tire nipple the valve 3 vis closed tightly, thus trapping the compressed the opposite end being closed by tlieendy Wall y 10b. The flanged periphery is clamped against the upper end'off the air chamber by any suitable means, as by a flanged internally threaded cap 15, an intermediate Washer being interposed so that the rotative movement of the cap, when screwed in place, Will not rub against the attaching or anc-hors ing flange 10- Any number of annular convolutions or folds may be employed, according to the desired rangeof movement. l ln Vorder that the ino-vement of the diaphragm shall be limited to an endivisemovement in order that the pressure of the air 4may be translated into an endWise movement ofthe diaphragm, the tubular portion thereof` is supported against lateral thrust caused by the compressed air by means of a series of appropriately formed rings. ,ln this case, as the air pressure is applied on the .exterior y of the tube, the tube-supporting members or rings are placed inside the ring and comprise eXteriorly tively small diameter to support the interior or convex convolutions, .and a series of thin# ner rings 13, of larger diameter that are inserted in the concavities formed by the folds. The botto-in is prevented :treni buck-v concaved rings 12, of rela- Y lou ling by means vof a dislr 11 of largefenough diameter to support the lowerniost fold. As these rings are separated from each other they are perfect-ly free tomove endvvise with the collapsing or extension movement of the tubular diaphragm tional resistance. Y Y

We prefer the arrangement by ivl ich air pressure isV applied tothe exterior of the tubular diaphragm so as to lhave an endivise compressing movement tliereoin although ive do not confine ourselves to such application of the pressure. f

rIhe cap 15'is provided with a concentric tubular neck or extension 15a partially closed at its upper end, as shown at 15b, to afford bearing support for a, transverse rotative arbor 21 to which secured a pinion 20 carrying'an exterior pointer 23, moving around a di-al plate 9A vwhich. is graduated and numn without offering fricthe bered to show the pressure measurement in poundsor other desired units ot' pressure.

Inside the tubular neck or extension 15a is mounted a freely movable slidable sleeve 16 of tubular form whose lowerend is threaded to receive a lnut 18b which is adjustably screwed on the threaded extension 18*L of a reciprocatory plunger 18, whose upper end portion is cut away to form a series of rack teeth 18C intermeshing withthe pinion 20. ,A helical compression spring 19, oif predetermined resistance, is interposed between the plunger 18 and the sleeve 16, said spring thrusting at one end against the ledges formed at 15b by the partially closed end of the tubular extension 15u, and thrusting at it-s other endagainst the adjustable tension nut 181. 16 and thethread on the reduced extension 18EL of the plunger are preferably made of t-he same pitch so that the nut, which is in the form of a spanner nut, may be adjusted to regulate the tension of the spring by compressing it to a greater or less degree, while at the same time preserving the .sameA relative position between the plunger and its surrounding sleeve.

An vannular casing 17, with one side perforated to receive the neck 15a oi the cap, is secured to the, device and its front wall,- forming the dial plate 24, is bored to allow the passage through it of the. arbor` 21. To

allow the insertion of the arbor with the pinion 2O secured to it, a bushing 22 is provided in the bearing part 15".

lt wilhtheretore, be seenthat uponA pressing the nipple seat of the pressure gauge upon the nipple of the tire stemcommunication is instantly established between the interior of the tire and the easing enclosing the air sealing diaphragm so that the air pressurefo'f the tire, in the .i-'orm shown, collapses `or shortens the tubular peripheral wall of the diaphW cin so that the plunger is moved upward l to its casing until a balance is established between the compression spring 19 and the air pressure exerted against Y the end wall of the diaphragm. This endwisemovement of the plunge-ris 'translated intero-tation ol the pointer relative to the dial. Vhen the tire gauge iste be removed from the tire stein, the air inlet valve is vclosed and traps the air so that none of the .confined air escapes and the dial reading is maintained 'i point established by the air pressure tire. To releasey the confined air the pressure of a finger against the slide button of the valve stem by the pin'affords a vent to allow the escape of air, so that the pointer returns to normal Yinitial position. f

f lt will be seen that the inlet valve is shifted to either closed or open position by the manually controlled member dispensingwith any valve'spring, and that the means Vtorrl"he internal thread of the sleeve nal sleeve 16, the compression spring 19 and the adjusting nut 43, engaging the threaded extension of a plunger are the same as the constructionv previouslyl described. rThe outer end of the tubular extension 40 is closed by an end-wall 40" which is centrally bored to vafford lateral bearingior a longitudinal plunge-r or spindle 42, whose lower end is reducedand screw threaded toy have adjustable engagement with the nut 43 after the manner above described.` The plunger or spindlehas anlenlarged head 43, provided itlh an annular I'iange 43h of sutlicient .depth and. proper circumference to surround the eX- terior ot a scale band 40, carriedr by the cap 40. The scale marking is of a well known type in which a'step seriesoi short lines,^cir

cumferentially offset, indicate the various degrees ot pressure with the appropriate numerals arranged to designate the lines, and

. the lower edge ofthe cap flange 43' will come to restv in alignment with one of these short scale lines, which indicates the number correctly indicative of the number of pressure exerted upon the gauge.. Y

To avoid frictional contact, which will be more orless subject to increase by thepresence of dust, a slight clearance is provided between the annular indicator 13b and the scale-band or cylinder, contact being prevented by the fact that. the plunger is supported against lateral play by the bearing 40h, and alsozby thehearing contactfbetween thefsleeve 16 andthe exterior ot'the .casing extension 40a. Hence the device is perfectly responsive to slight changesk in pressure and, like the other form described, is noti subjectV to derangement or inaccuracy through changes in the co-eficient of elasticity iii-thc diaphragm, nor is it subject to changes due to variations in frictional engagement because the indicator is vsupported and guided yhy interior bearings that are not exposed to an accumulation of dust. i f

In both cases the tire pressure reading preserved i'orfconvenient mspection by trr p ing the air and not the use of some fric tionally retained member which is frictionally engagedk and, therefore, prevents the sensitiveness ot the pressure gauge. l

If accurately constructed theV device will be very sensitiveA to variations in pressure and will give accurate pressure indications indefinitely, and does not require careful and delicate handling to prevent derangement ot pounds Cir (lil

seated after it has been moved to closed position. This is important since the body of air contained in the gauge is so small that even an instants delay inclosing the inletvalve when breaking the connection will vent the casing enough to materially diminish its pressure.

What we claim is:

l. A pneumatic-tire pressure gauge embracing in combination an air-confining chamber adapted for temliorary-application to a tire stem, a casing secured to the open end of said chamber, an air-confining diaphragm of pliable fabric interposed between the chamber and the casing, an extensible spring-pressed plunger mounted in the casing to oppose a yielding thrust against said diaphragm to counter-balance the air pressure, a spring-tensioning nut interconnecting the extensible members of the plunger to permit lextension of the Aplunger without affecting the spring tension and to permit the tensioning of the spring without extending the lunger, and a pressure scale indicator controlled by the Amovement of the plunger.

i2. In a pressure gauge, the combination with a compressed airchamber adapted for application toV a tire stem, a plunger casing secured thereto, a pressure-responsive endwise collapsible diaphragm interposed .to irevent the escape of'ai-r from the chamber to the casing, a spring-pressed plunger mounted in the casing to oppose yielding resista-nce to the air pressure thereon, said plunger having bearing engagement with an interior sort-ion of the casing to maintain a lstraight line' reciprocation, a hollow capsecured to the upper end ofthe plunger with its peripheral wall overlapping thev outer wall of the casing, said outer wall being provided with a pressure-indicating scale serving, in conjunction with said cap, to measure the air pressure upon the diaphragm.-

8. In a pressureindicating device, a pressure-actuated air seal for a compressed air chamber, embracing in its construction a tubular member of pliable fabric impervious to air having a closed end and having its circumferential wall formed with annular internal and external. folds in alternation, and a series of spaced pressure-'resisting members adapted to engage respectively convex and concave faces of successive folds to pre! vent lateral displacement thereof under pressure of the air, while allowing the closed end of the tubular member to move'freely endwise to different positions in correspondence with the change vin air pressure.

4t. In a pressure indicating device, a pressure-actuated air seal diaphragm embracing In a tire pressure gauge, the combination with a compressed chamber, of a tubular diaphragm of pliable air-proof fab-A ric whose open end edge isisecured Ato said chamber to confine air therein and whose closed free' end forms a yielding seat for receiving the thrust of a movable springpressed plunger, the circumferential wall. of

said tubular diaphragm being formed in an-v nular folds to render it extensible andcontractible endwise without requiring stretch of the fabric, and means for preventing both the convexand the concave inner faces of said folds of the tubular wall from buckling underthe external pressure of the compressed air without impairing freedom of contracting and expanding movements. f i

6. ln a tire pressure gauge thecombination with a compressed air chamber, o f a tubular diaphragm of flexible'impervious fabric secured peripherally at its open end to said air chamber, said tubular diaphragm havingfits free end closed to form a seat to yieldingly oppose the thrust of an interiorlyvdisposed Y spring-pressed plunger and having itscircumferential4 wall formed in annular vfolds to render it collapsible and extensible independently of` any stretch of its fabric, and means arranged at intervals inside the folds of the tubular wall to reinforce both the inwardly and the outwardly turned VfoldsV against collapsingunder pressure ofthe air, while leaving 1t free to expand and contract to establish a balance between theplunger and the air pressure.

7. VIn a tire pressure gauge, the combination with a compressed air casing adapted to be applied to a tire, to admitair from the tirer into the casing, of a movable pressure indica-- tor, aspring-pressed member arranged rto yieldingly sustain and counterbalance the pressure of air admitted, and acting to move the pressure indicator'to different' pressureindicating positions in conformity tothe air pressure in the tire, and manually operated means for trapping the compressed air adias mitted from the tire into the casing to preserve the pressure reading after removal of the gauge from the tire.

8. In a tire pressure gauge, the combination With a casing forming a pressure tight chamber7 and provided with a. oompressible seat adapted to form an airtight joint when pressed against the tire stem nipple to un seat 'the tire valve, an inlet valve arranged in said casing'to normally admit air Jfrom the tire to the easing, an externally projecting manually operated valve-shifting device for closing and opening said valve at will, a movable pressure-responsive member and-a pressure indicator Wnose position is determined by the position of the pressure responsive nieniber. e

9. ln a tire pressure gauge, thev combination of a hollow casingl forming a Compressed air chamber and longitudinally bored to form a valve chamber closed at one end said valve chamber being` provided with a lateral intake duct arranged to admit air from a pneumatic tire, and being' provided with a longitudinal air passage affording communication between said lateral duct and the open end ol" said valve chamber, a valveslidablyv7 mounted in said valve chamber and having', at the inner end of its stem, an enlarged head formed to seat against the flared open end ot' said valve chamber to seal said longitudinal air passage, anda valve-shifting means arranged to be manually operated and having connection with the valve stem to open and close the valve at will, pressure-indieating,r means and means responsive to the pressure of the air confined in said casing by the closing of the valve, to maintain said indicating means at pressure-indieatinfr;r position.

10. In a tire pressure gauge adapted to be applied to a pneumatic tire, the combination of a vhollow casing having a longitudinal bore closed at its outer end to form a valve chamber, and provided with a lateral inlet duct in communication With a longitudinal air passage on one side of said valve chamber to admit air to the interior chamber of the easing and on its opposite side having a lateral'slot, an intake valve having an enlarged head at its inner end to closev said air passage when moved against its seat, and means eX- tending through saidslot to manually shift the valve from open to closed position.

11. n a pressure gauge. for pneumatic tires, the combination with a hollow casingl adapted to be appliedto a tire stem to unseat the tire valveA and admit air into the casing, pressure-responsive means, pressure indicating means actuated by said pressure-responsive means or indicating the pressure of the air admitted from the casing7 and meansfor entrapping` the air in said casingl operable in advance of the interruption of the connection between the gauge and the tire whereby the admitted air is confined in the casing Without loss in order topreserve unimpaired p1'es.

sure indication after the gauge is removed.

In Witness whereof, We have subscribed the above specification.

JOHN E. KENNEDY.

M. A. KENNEDY. 

